Apple has released Mountain Lion, aka Mac OS X 10.8, the latest version of its Mac OS X desktop operating system, as a download from its Mac App Store for £13.99 ($19.99 in the US).

The company says that it includes more than 200 new features (a figure that has been fairly consistent over other OS X releases), though the most important for many users will be the new Gatekeeper feature - to prevent malicious apps downloaded from the web from infecting machines - and the addition of iCloud functionality to many applications.

It also brings a Notification Centre which mimics that found in the iOS software on the iPhone, voice dictation, AirPlay Mirroring to send audio or video streams to compatible devices from a Mac, and the Game Center function found on the iPhone, iPad and iPod Touch. A forthcoming update will add Facebook integration to apps.

The release was foreshadowed by Apple's chief executive Tim Cook as he announced the company's financial results for the second calendar quarter on Tuesday night.

As usual, the arrival of the new version has drawn a plethora of reviews: here's our collection of the runners and riders.

In a nutshell, OS X 10.8 is a generous helping of iOS-friendly syncing apps and services, with a sidebar of unfortunately poor Messages and a grab bag of 'most wanted' features and tweaks to Lion.

It's absolutely worth the $20 price tag to upgrade, as there is more good here than bad, and that's super cheap.

As Panzarino points out, the idea that Apple is trying to turn OSX into iOS doesn't make sense, since the latter came from the former (under the direction of Scott Forstall, now head of iOS). He notes:

Mountain Lion continues the unification of Apple's platforms by adding even more features found on iOS to OS X. But it also contains a healthy sprinkling of small improvements and polishing notes that feel very reminiscent of its Snow Leopard release. That was an OS designed to polish up the rough edges of Leopard, a major game-changing release that was big on ideas and a bit short on execution.

His conclusion? "OS X will get more features that sync seamlessly with portable devices, that work logically and without a lot of tweaking. It will come at the expense of easy tweaking and massaging, but it will make users lives simpler."

Snell gives it 4.5 mice (out of 5), noting that "At $20, Mountain Lion is Apple's cheapest OS X upgrade since version 10.1 was free 11 years ago". He points to how much tighter iCloud integration is (you're asked for an iCloud ID when you first set up; then documents you've created and saved to iCloud are stored and altered there).

The traditional file system is beginning to be obscured - a path Apple went down in the Lion release when it hid the /user/Library directory (it's still there, like C:\Windows, but takes some accessing). "Many expert users will blanch at the concept of not using the traditional file system, but Apple believes that most computer users struggle with finding files and traversing file systems," Snell notes.

Gatekeeper has the potential to be the most important change. Developers can apply for a cryptographically signed certificate; though Apple doesn't check who applies, it can revoke a certificate - so that if you choose only to allow apps that have Gatekeeper-signed certificates to run, anything that turns out to be malware can be killed by Apple. However, it's not a malware fix - and there could still be holes.

Apple Mail gets improvements (such as a VIP filter - only see emails from particular people, when you choose). And there are plenty more. Snell's conclusion:

Even prerelease builds were far more stable than I've come to expect from OS X betas, leading me to wonder if Apple's new annual schedule is leading to more careful incremental updates (with fewer bugs) rather than great leaps (with more, nastier bugs).

He points out that it's barely a year since 10.7 ("Lion") and the announcement of the first beta in February was a surprise too. He too says there's barely any reason to consider the cost; compared to the $100 (or £80) that Mac OS X upgrades used to cost, this is light.

His advice: don't being in a hurry to upgrade:

Some nasty problems have been known to slip past Apple's testers and into the wilds, and something you rely on - some small utility or a printer driver or somesuch - may not yet be updated to work with the new OS.

. That - and the advice to make backups and test that they work (ie you can boot from them, and reinstall them) are probably the soundest suggestions you'll hear around any OS release on any platform.

"A roaring success?" asks Miles carefully. The only UK reviewer who got to see the first beta in February, he's also the only one we've seen (fingers crossed: so far) who puts Mountain Lion into its proper context, which is in comparison with Microsoft's Windows 8:

Having now played with both the Windows 8 Previews and OS X Mountain Lion extensively over the past couple of months, what's fascinating is that both are gunning for the same finish line, but with at times, very different approaches.

Mountain Lion is a slow movement though to a complete transition rather than Microsoft's approach with Windows 8 that is very much a head-first ordeal.

Like (we suspect) many, he dislikes the harking back to physical objects that the apps aren't - torn pages for Notes, for example. " Considering there is nothing quaint about the metal-clad devices Apple puts the software on, this disconnect is getting old and boring." That's basically his only complaint; at the price, an upgrade is money "well spent - moreso if you use an iPhone or an iPod."

Known in the Mac community for his book-length OS X reviews (in fact, Ars Technica offers them as paid-for ebooks; or you can page through the 24 pages of the review), Siracusa shines spotlights on the places nobody had thought of, and then shines more spotlights on the other bits too. Each is a sort of War and Peace of the product. This review weighs in at 26,000 words, which as Marco Arment points out, is back to normalcy for him, after a gigantic 40,000-word treatise on Mac 10.4 ("Tiger") in April 2005.

If you have time to spare, Siracusa's review will probably fill the time either while you wait for Mountain Lion to download, or while you wait for other people to download it and discover the bugs.

Here's the direct Apple Store link; you won't be able to download it unless your machine is compatible. It's a 4GB download, and you need 8GB of free space.